Encyclopedia of Medieval Philosophy

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al-Kindī, Abū Yūsuf Yaʿqūb ibn Isḥāq

  • Peter AdamsonEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-94-024-1151-5_289-2


Al-Kindī (c. 800–870) was the first figure in the Arabic philosophical tradition to make explicit and extensive use of Greek ideas. He is thus often described as the first philosopher of this tradition. He also oversaw the work of translators who rendered works by Aristotle, Plotinus, Proclus, and others into Arabic. His own writings, usually in the form of epistles to patrons, range widely over the topics of Greek philosophy and science. His fusion of Aristotelianism with Neoplatonism was intended to be congenial to Islam, and this approach influenced several other authors of the early Arabic philosophical tradition.

Abū Yūsuf Ya‘qūb ibn Isḥāq al-Kindī was probably born around 800 into an important family: his father was the governor of Kūfa in Iraq, and al-Kindī could trace his lineage back to a companion of the Prophet. To highlight his origins in the tribe of Kinda, and perhaps the failure of the Arabs to produce other prominent philosophers, he was later given the sobriquet “philosopher of the Arabs.” He himself was a highly placed intellectual, serving as tutor to the son of the Caliph al-Mu‘taṣim (who reigned from 833–842). We know that he died after 866, the date of an event mentioned in one of his astrological works; his death date is usually put at around 870–873.

Al-Kindī’s association with the caliphal family is connected to his important role in the translation movement (for which see Gutas 1998; Endress 1987/1992). He was apparently not himself a translator but coordinated and revised the work of a translation circle whose members seem to have been mostly Christians of Syrian extraction. This so-called Kindī circle (see Endress 1997) produced Arabic versions of Aristotle (for instance, the first translation of the Metaphysics) and, famously, Plotinus and Proclus. A redaction of their version of Plotinus came to be known as the Theology of Aristotle, the most important source for Neoplatonic ideas in the Arabic-speaking world (see Adamson 2002b). Their version of Proclus (on which see Endress 1973) would be influential in the Latin world, in a version later called the Book of Causes (Liber de causis: see D’Ancona 1995).

This circle of translators seems to have produced two kinds of translations: painfully literal ones and remarkably free paraphrase versions. Of the literal type, the most significant is their version of Aristotle’s Metaphysics, ascribed to one Usṭāth and preserved in the lemmata of Averroes’ Long Commentary for some books of the Metaphysics. The paraphrase translations, which include their Arabic renderings of Plotinus and Proclus, revise and rework the philosophical content of the texts and also reorder the texts, though the extent to which the reordering was done already in Kindī’s circle is a matter of controversy. Part of the point of the reworking was to make these works seem useful for a contemporary audience. Most obviously, the Neoplatonic First Principle is assimilated to a Creator God.

The same motivation guides many of al-Kindī’s own philosophical works, which are edited in Abū Rīda (1950, 1953) (see also Rashed and Jolivet 1998) and translated in Adamson and Pormann (2012). These philosophical treatises, usually written as epistles to the caliphal family and other patrons or colleagues, constitute a sizable corpus, especially if they are taken together with extant works on a range of scientific topics. (Particularly well represented are astrology, optics, mathematics, meteorology, medicine, and music.) But much of his prodigious output is lost. We have a list of his works in the Fihrist of the tenth-century bookseller Ibn al-Nadīm. Like the extant corpus, this list indicates that al-Kindī worked in an astonishing variety of fields, ranging from metaphysics to the production of perfume and swords. This eclecticism is in itself a sign of al-Kindī’s desire to satisfy the needs of his cultivated audience (see Rosenthal 1942).

The most famous of al-Kindī’s more narrowly “philosophical” works is On First Philosophy (translated in Ivry 1974 and Rashed and Jolivet 1998), which draws extensively on Aristotle, especially the Metaphysics, but also weaves in themes from Neoplatonic texts and borrows arguments from John Philoponus. On First Philosophy is only partially preserved: we possess the “first part,” which is divided into four sections. Al-Kindī’s best-known philosophical ideas are contained in this work.

In Section 1, al-Kindī mounts a spirited defense of the utility and acceptability of using ideas drawn from the Greek tradition and criticizes detractors of “foreign” philosophy. It is unclear who these detractors might be, though Ivry (1974) speculates that they were contemporary theologians, such as those collectively described as “Muʿtazilite.” Adamson (2007a, p. 25) suggests that the opponents are more likely to be traditionalists who took a literalist attitude toward scriptural descriptions of God. One reason to think this is that al-Kindī’s patrons in the caliphal court supported the Muʿtazilites in their argument against the traditionalists over the question of the eternity of the Qurʾān (see further Adamson 2003).

That debate may be somehow related to the topic of Section 2, where al-Kindī argues at length that the created world is not eternal. Here al-Kindī uses and reworks arguments drawn from John Philoponus’ attack on Aristotle (see Davidson 1969). The thrust of these arguments is that if the cosmos were eternal a parte ante (i.e., if it has existed for an infinite time), then this would make the cosmos an “actual infinity,” analogous to an infinitely large body. Al-Kindī thus argues, for instance, that if the cosmos is finite in magnitude, it cannot have an infinite quantity predicated of it. But time is a quantity, so only a finite amount of time can be predicated of the cosmos. Now Aristotle too regarded the actual infinite as impossible. He held, however, that an eternity of time would constitute only a potential infinity (the sort of infinity involved in counting up through the integers: the process is indefinite but never actually reaches an infinite number). Thus, al-Kindī, following Philoponus, disagrees with Aristotle primarily in that he believes an ex parte ante eternal cosmos would constitute an actual, rather than potential, infinity.

In Sections 3 and 4, al-Kindī gives a complex argument for a “true One” who is the cause of unity in all other things. As is made explicit at the close of the extant text, this true One is the God of Islam. Al-Kindī also argues that this true One transcends characterization by the maqūlāt, that is, things that can be said. These terms include the predicables from Porphyry’s Isagoge and also part, whole, relation, motion, and soul. Finally, the true One is higher than the intellect: this is a departure from Aristotle but agrees with Plotinus. The reason given for denying all these terms to God is that they imply both multiplicity and unity. Indeed, the argument for God’s existence given in Section 3 is based on the claim that all created things are characterized by both unity and multiplicity. Al-Kindī then argues that some cause is required to explain this association of unity and multiplicity. The cause must be entirely one and not many at all, so that it is outside the set of things that are both one and many.

Al-Kindī also expresses this idea by saying that while God is “essentially” one, that is, one but not at all many, other things are “metaphorically” one, that is, both one and many. A similar idea is found in a very short, perhaps fragmentary text called On the True Agent. Here the point is that only God is truly an Agent, because other things are acted upon, even if they also act. Al-Kindī thus describes God’s first effect as an intermediary for God’s creative action. This too may be an inheritance from the Neoplatonic translations produced in his circle.

On the other hand, in works on cosmology, al-Kindī presents not a Plotinian intellect but the heavenly bodies, as the chief instrument by which God indirectly brings about a providentially ordered cosmos. Al-Kindī follows the Aristotelian tradition in seeing the world below the sphere of the moon as consisting of the four elements, air, earth, fire, and water. The heavenly bodies, by contrast, are made of an indestructible fifth element. Al-Kindī devotes an epistle to arguing for this claim, apparently unconcerned or unaware that it was a key part of Aristotle’s arguments for the eternity of the world, and was attacked by Philoponus in his Against Aristotle. He does, however, add the caveat that the heavens exist without being generated or destroyed, but only for as long as their Creator ordains.

Because heavenly motion brings about the mixture of the four sublunary elements, it is the heavens that are directly responsible for the well-ordered world we live in. As al-Kindī puts it, they are the “proximate cause of generation and corruption,” while God is the remote cause, exercising His providence by commanding the heavens to move in the appropriate way. Though al-Kindī draws these ideas from Aristotle and his commentator Alexander of Aphrodisias, he extends the theory in several ways. For example, he uses the theory to interpret a verse from the Qurʾān which states that even the stars “prostrate” themselves before God. Al-Kindī also discusses in detail how the cosmological theory can work in practice, arguing for the effects of heavenly motions on weather and the tides. His extensive work in astrology presupposes the cosmology described in his more Aristotelian epistles. The same theory is used by his associate, the great astrologer Abū Ma‘shar (see further Adamson 2002a, 2007a, chap. 8).

By contrast, al-Kindī is not clear on how God’s creative activity relates to immaterial things, notably the human soul. He does describe the soul as a “light from the light of the Creator” in a doxographical work, the Discourse on the Soul. But the emphasis in this and other works of psychology is usually on the immateriality of the soul and its essentially intellective nature. In one short epistle, for example, he uses ideas from Aristotle’s Categories to prove that the soul is immaterial. The argument turns on an identification between soul as the form of the body and the form that is the species of mankind. Since, in general, species are immaterial substances (this follows Aristotle in the Categories, though al-Kindī omits the point that species are only “secondary” substances), the soul too will be an immaterial substance.

In the more famous Letter on the Intellect, a forerunner of works on the intellect by al-Fārābī, Avicenna, and others, al-Kindī classifies intellect (‘aql) into four types: “first,” potential, actual, and acquired. The “first” intellect is separated from human soul and is apparently to be identified with the maker intellect of Aristotle, De Anima III.5 (we know from On First Philosophy that this is not to be identified with God). The other three are aspects or states of the human intellect. Humans think by taking on an intellectual form which is seated in the first intellect. Before they do this, they have a merely potential intellect. Actual intellect refers to the human intellect when it is actually grasping such an intellectual form. For al-Kindī the term “acquired intellect” means simply the intellectual forms which one has already learned and can then think about at will – like a storehouse of intelligibles within the soul. This is in contrast with al-Fārābī’s use of the term to mean the full attainment of all the intelligibles.

A puzzle about al-Kindī’s epistemology is how this theory of intellect relates to his acceptance of the Platonic theory of recollection, which he discusses in a short epistle (see Endress 1994). More generally there is an unclarity about the role of sense experience in al-Kindī’s epistemology. It usually seems that for him there is a strong divide between the intelligible and sensible realms and that the human soul properly belongs on the intelligible side. This picture is basically confirmed, though with greater nuance, in texts dealing with faculties between intellection and sensation. The most important of these is a work on prophetic dreams, based closely on the Parva Naturalia. Al-Kindī here makes dreams a product of the imaginative faculty and discusses the interaction of this faculty with the body. But significantly, and unlike Avicenna, for instance, he argues that the imagination does not use the brain or indeed any organ directly. Instead, it belongs to the immaterial soul. It is able to receive signs about the future precisely because it is ontologically closer to intellect than to the body. Despite these differences from Avicenna, he does anticipate the latter’s theory of the internal senses, but only in a classification found in a work on music (Adamson 2007a, p. 142).

Music is one area where al-Kindī deploys his expertise in mathematics. This is unsurprising since music was considered part of the mathematical curriculum already in antiquity. More distinctive is his use of mathematical methods of argument in purely philosophical contexts; on this see Gutas 2004. Aside from methodology, one might think of the Pythagorean flavor of his portrayal of God as a pure One (though he is careful to contrast God to the one that generates number). Al-Kindī also uses mathematics in discussing cosmology, for instance, to demonstrate that the cosmos consists of concentric spheres (the heavens and elements), and in explaining why the ancients associated the heavens and elements with the Platonic solids. This latter point is clearly indebted to the Timaeus, though the means of influence is unclear. We do know that one Pythagorean work on mathematics was known to and used by al-Kindī, namely, Nicomachus of Gerasa’s Introduction to Arithmetic.

He also brings his mathematical sensibilities to bear on medicine, in an influential work on calculating the effects of compound drugs (translated into Latin as De Gradibus). He applies geometry to problems of optics, in this following the tradition of mathematical optics already explored by Euclid and Ptolemy. His theory of light is an important precursor of the visual theory of Ibn al-Haytham (d. 1040). The success of geometry in optics may have encouraged him to extend a theory of “rays” to deal with a broad array of physical phenomena. We find such a theory on De radiis, a work preserved only in Latin and influential on medieval theories of magic. Though this work is ascribed to al-Kindī, its authenticity is disputed. (For further discussion of al-Kindī’s mathematically inspired works, see Travaglia 1999 and Adamson 2007a, chap. 7. For his works on optics, see Rashed 1997.)

We know from the Fihrist that al-Kindī wrote extensively on practical philosophy, but unfortunately most of this output is lost. We are left with only a few relevant works, the longest and most influential of which is On Dispelling Sorrow (see Druart 1993; Mestiri and Dye 2004; Adamson 2007a, chap. 6). In general, al-Kindī’s ethical outlook is simple and uncompromising: turn away from the things of the body and concentrate on the “world of the intellect.” This is already clear from the aforementioned Discourse on the Soul. But in On Dispelling Sorrow, al-Kindī adds to the intellectualist picture familiar from his psychological works, giving the reader encouragement with an abundance of anecdotes and maxims. A couple of these are drawn from his anthology of sayings and witticisms ascribed to Socrates, which is an early example of the so-called wisdom literature, an often-overlooked means of cultural contact between literary Arabic and the Greek philosophical tradition.

Finally, mention should be made of two propaedeutic works by al-Kindī or his circle, which are intended as guides to the Greek philosophical tradition for his Arabic-speaking audience. First, On the Quantity of Aristotle’s Books, which provides a picture of al-Kindī’s knowledge of the Aristotelian corpus. The structure into which he puts his overviews of each Aristotelian work tells us something about how he saw the Greek philosophical curriculum: he follows the tradition of seeing theoretical science as divided into three parts, dealing with bodies, immaterial things that are related to bodies (i.e., souls or mathematical entities), and wholly immaterial things (notably God). His summaries show an uneven knowledge of Aristotle’s corpus, to the point where he can at times add nothing beyond the title. But there are longer discussions of the Categories and Metaphysics, for instance, works which we know he used in his own writings.

Second, there is, On the Definitions and Descriptions of Things, a work preserved in several very different versions. Each version comprises a list of philosophical terms with definitions. The terms defined seem to be drawn from Greek sources, but the terms themselves are Arabic. This shows that al-Kindī and his circle realized the need to produce a new Arabic technical vocabulary based on the Greek vocabulary of their source texts. They realized also that this new Arabic terminology would not be easily understood by their audience. On Definitions can thus be seen as a guide to the new language of philosophy in Arabic, or falsafa (which, as it happens, is one of the two terms with the longest definitions, the other being “virtue”). The terminological innovations of the Kindī circle had mixed success. Some of their technical words were taken up in the later tradition, while others were dropped. But as mentioned above, the translations they produced were influential.

The influence of al-Kindī’s own thought was confined largely to a group of authors who might be called the “Kindian tradition” (see Adamson 2007b). These include, in the first instance, attested students and associates of al-Kindī himself: al-Sarakhsī (d. 899), Abū Zayd al-Balkhī (d. 934), and the aforementioned astrologer Abū Ma‘shar al-Balkhī (d. 886). Abū Zayd was an important conduit for the Kindian tradition, since he taught the well-known philosopher Abū l-Ḥasan al-‘Āmirī (d. 922) and the more obscure Ibn Farīghūn (tenth century). Apart from first- and second-generation students, figures influenced by al-Kindī include the Jewish thinker Isaac Israeli (d. c. 907) and the historian and Neoplatonist Miskawayh (d. 1030), both of whom quote from al-Kindī and texts produced in his circle.

The Kindian tradition is distinctive, first of all, geographically: most of the thinkers just mentioned were from Central Asia (e.g., Balkh and Sarakhs). Intellectually, they are distinguished by their openness to a wide range of disciplines, including Muslim speculative theology (kalām) and the finer literary arts. In both respects they can be contrasted to the tenth-century circle of Aristotelian thinkers in Baghdad, who included the famous al-Fārābī. But perhaps because of Avicenna’s disdain for the Kindian thinkers, al-Kindī’s influence seems to peter out around the end of the tenth century.



Primary Sources

  1. Abū Rīda, M. (Ed.) (1950/1953). Al-Kindī. Rasā’il al-Kindī al-falsafiyya, 2 vols. Cairo: Dār al-Fikr al-‘Arabī.Google Scholar
  2. Adamson, P., & Pormann, P. E. (Trans) (2012). The philosophical works of al-Kindī. Karachi: Oxford University Press.Google Scholar
  3. Ivry, A. (1974). Al-Kindī’s metaphysics. Albany: SUNY.Google Scholar
  4. McGinnis, J., & Reisman, D. C. (Eds. & Trans) (2007). Classical Arabic philosophy: An anthology of sources. Indianapolis: Hackett.Google Scholar
  5. Mestiri, S., & Dye, G. (2004). Al-Kindī: Le moyen de chasser les tristesses et autres textes éthiques. Paris: Fayard.Google Scholar
  6. Rashed, R. (1997). Oeuvres philosophiques & scientifiques d’al-Kindī: vol 1: L’Optique et la catoptrique. Leiden: Brill.Google Scholar
  7. Rashed, R., & Jolivet, J. (1998). Oeuvres philosophiques & scientifiques d’al-Kindī: vol 2, Métaphysique et cosmologie. Leiden: Brill.Google Scholar
  8. Ritter, H., & Walzer, R. (1938). Uno scritto morale inedito di al-Kindī. Rome: Reale Accademia Nazionale dei Lincei.Google Scholar

Secondary Sources

  1. Adamson, P. (2002a). Abū Ma‘shar, al-Kindī and the philosophical defense of astrology. Recherches de philosophie et théologiemédiévales, 69, 245–270.CrossRefGoogle Scholar
  2. Adamson, P. (2002b). The Arabic Plotinus: A philosophical study of the theology of Aristotle. London: Duckworth.Google Scholar
  3. Adamson, P. (2003). Al-Kindī and the Mu‘tazila: Divine attributes, creation and freedom. Arabic Sciences and Philosophy, 13, 45–77.CrossRefGoogle Scholar
  4. Adamson, P. (2007a). Al-Kindī. New York: Oxford University Press.Google Scholar
  5. Adamson, P. (2007b). The Kindian tradition: The structure of philosophy in Arabic Neoplatonism. In C. D’Ancona (Ed.), The libraries of the Neoplatonists (pp. 351–370). Leiden: Brill.CrossRefGoogle Scholar
  6. D’Ancona, C. (1995). Recherches sur le Liber de causis. Paris: Vrin.Google Scholar
  7. Davidson, H. A. (1969). John Philoponus as a source of medieval Islamic and Jewish proofs of creation. Journal of the American Oriental Society, 89, 357–391.CrossRefGoogle Scholar
  8. Druart, T.-A. (1993). Al-Kindī’s ethics. The Review of Metaphysics, 47, 329–357.Google Scholar
  9. Endress, G. (1973). Proclus Arabus. Zwanzig Abschnitte aus der Institutio theologica in arabischer Übersetzung. Beirut: Steiner.Google Scholar
  10. Endress, G. (1987/1992). Die wissenschaftliche Literatur. In H. Gätje (Ed.), Grundriss der arabischen Philologie (vol 2, pp. 400–506, Vol. 3(supplement), pp. 3–152). Wiesbaden: Ludwig Reichert.Google Scholar
  11. Endress, G. (1994). Al-Kindī über die Wiedererinnerung der Seele. Oriens, 34, 174–221.CrossRefGoogle Scholar
  12. Endress, G. (1997). The circle of al-Kindī. In G. Endress & R. Kruk (Eds.), The ancient tradition in Christian and Islamic Hellenism (pp. 43–76). Leiden: Research School CNWS.Google Scholar
  13. Gannagé, E. (2016). Al-Kindī, Ptolemy (and Nicomachus of Gerasa) revisited. Studia Graeco-Arabica, 6, 83–112.Google Scholar
  14. Gutas, D. (1998). Greek thought, Arabic culture: The Graeco-Arabic translation movement in Baghdad and early ‘Abbāsid society (2nd–4th/8th–10th centuries). London: Routledge.CrossRefGoogle Scholar
  15. Gutas, D. (2004). Geometry and the rebirth of philosophy in Arabic with al-Kindī. In R. Arnzen & J. Thielmann (Eds.), Words, texts and concepts cruising the Mediterranean Sea: Studies on the sources, contents and influences of Islamic civilization and Arabic philosophy and science (pp. 195–209). Leuven: Peeters.Google Scholar
  16. Jolivet, J. (1971). L’Intellect selon Kindī. Leiden: Brill.Google Scholar
  17. Rosenthal, F. (1942). Al-Kindī als Literat. Orientalia, 11, 262–288.Google Scholar
  18. Rudolph, U., Hansberger, R., & Adamson, P. (2016). Philosophy in the Islamic world: 8th–10th century. Leiden: Brill.Google Scholar
  19. Travaglia, P. (1999). Magic, causality, and intentionality. The doctrine of rays in al-Kindī. Turnhout: Micrologus.Google Scholar

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Authors and Affiliations

  1. 1.Philosophy DepartmentLMU MunichMunichGermany